U.S. patent application number 10/748174 was filed with the patent office on 2005-07-21 for distributed clumping of part-length rods for a reactor fuel bundle.
Invention is credited to Fawcett, Russell M., Fujimaki, Shingo, Goto, Daisuke, Kunz, Cary L., Stachowski, Russell E., Trosman, Lukas.
Application Number | 20050157837 10/748174 |
Document ID | / |
Family ID | 34104872 |
Filed Date | 2005-07-21 |
United States Patent
Application |
20050157837 |
Kind Code |
A1 |
Trosman, Lukas ; et
al. |
July 21, 2005 |
Distributed clumping of part-length rods for a reactor fuel
bundle
Abstract
A reactor fuel bundle includes both full-length fuel rods and
part-length fuel rods. The part-length rods are clumped in two
groups--a first rod group surrounds one or more water passages
which are generally centrally disposed in a channel of the fuel
bundle, and a second rod group is distributed about an inner
perimeter wall of the channel.
Inventors: |
Trosman, Lukas; (Wilmington,
NC) ; Kunz, Cary L.; (Wilmington, NC) ;
Stachowski, Russell E.; (Wilmington, NC) ; Fawcett,
Russell M.; (Atkinson, NC) ; Fujimaki, Shingo;
(Yokohama-Shi, JP) ; Goto, Daisuke; (Kamakura-shi,
JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 8910
RESTON
VA
20195
US
|
Family ID: |
34104872 |
Appl. No.: |
10/748174 |
Filed: |
December 31, 2003 |
Current U.S.
Class: |
376/435 |
Current CPC
Class: |
Y02E 30/30 20130101;
G21C 3/328 20130101; G21C 3/322 20130101; Y02E 30/38 20130101; Y02E
30/31 20130101 |
Class at
Publication: |
376/435 |
International
Class: |
G21C 003/32 |
Claims
1. (canceled)
2. The fuel bundle of claim 22, wherein a void formed above each of
the part-length rods together with the fluid passage each define a
water trap when containing a fluid, to trap neutrons.
3. The fuel bundle of claim 22, further comprising: a generally
parallel configuration of the fuel rods; and at least one support
member connected to the channel to equidistantly space proximate
ones of the fuel rods in the generally parallel configuration.
4. The fuel bundle of claim 3, wherein the opposed ends comprise: a
lower feed end having a first support structure for receiving a
lower end of each of the fuel rods and the fluid passage; and an
upper discharge end having a second support structure for receiving
an upper end of each of the full-length fuel rods and the fluid
passage.
5. The fuel bundle of claim 4, wherein the channel further
comprises: a connecting structure for supporting the channel.
6. The fuel bundle of claim 22, wherein the second rod group
further comprises a plurality of subgroup pairs of the part-length
rods, each subgroup pair positioned proximate to the perimeter
wall.
7. The fuel bundle of claim 6, wherein the second rod group further
comprises both pairs and individual ones of the part-length rods,
the pairs and the individual ones of the part-length rods spaced
about the perimeter wall.
8. (canceled)
9. The fuel bundle of claim 23, wherein the channel includes an
inlet end, an outlet end oppositely positioned from the inlet end,
and at least one fluid passage defining a tube rigidly connectable
to the perimeter wall and extending between the inlet end and the
outlet end.
10. The fuel bundle of claim 23, wherein the channel has a
rectangular cross-section.
11. The fuel bundle of claim 23, wherein proximate ones of the fuel
rods in each of the rows and columns have a fixed spacing
therebetween.
12. (canceled)
13. The fuel bundle of claim 12, wherein the second rod group
further comprises both pairs and individual ones of the part-length
rods.
14. The fuel bundle of claim 23, wherein each part-length fuel rod
of the pairs of part-length fuel rods of the second rod group
operably forms one of the face-to-face pairs with one of the
full-length fuel rods.
15. The fuel bundle of claim 9, further comprising a circular
shaped tube defining each fluid passage.
16. The fuel bundle of claim 9, further comprising: a rectangular
shaped tube defining each fluid passage and having the first rod
group disposed adjacent thereto.
17. A fuel bundle providing multiple length fuel rods, comprising:
a channel having four interior walls and a proximately positioned
pair of water passages each defining a tube rigidly supported to
the channel; a plurality of full-length fuel rods rigidly supported
within the channel, the full-length fuel rods generally disposed
face-to-face in column/row alignment, including a first set
proximately positioned at the four interior walls, and a second set
separated from the four interior walls by the first set; a
plurality of first subgroups each having two proximately positioned
part-length fuel rods, each first subgroup disposed adjacent one of
the four interior walls and interposed with the first set of
full-length fuel rods; a pair of second sub-groups of part-length
fuel rods each second sub-group positioned proximate to both the
water passages; and each of the second sub-groups of part-length
fuel rods including three part-length fuel rods configured in a
triangle shape; wherein any of the part-length fuel rods of the
first sub-groups are spatially separated from any of the part
length fuel rods of the second sub-groups by at least two of the
full-length rods.
18. The fuel bundle of claim 17, wherein the channel further
comprises: at least one lower support operable to rigidly support
and space the full-length fuel rods, the part-length fuel rods, and
the water passages; and at least one upper support operable to
rigidly support and space the full-length fuel rods and the water
passages.
19. The fuel bundle of claim 18, wherein the channel further
comprises at least one intermediate rod support disposed between
the lower support and the upper support, positioned to rigidly
support and space the full-length fuel rods, the part-length fuel
rods and the water passages.
20. The fuel bundle of claim 17, wherein the channel further
comprises a body lifting member.
21. The fuel bundle of claim 17, wherein each water passage has a
shape selected from the group consisting of a circle, an oval, a
square, a rectangle, a cruciform and a free-formed shape.
22. A fuel bundle, comprising: a channel having a perimeter wall
and opposed ends; a pair of fluid passages each defining a tube
rigidly supported within the channel and extending between the
opposed ends, the fluid passages aligned proximate to each other
and each proximate to a longitudinal centerline of the fuel bundle;
a plurality of fuel rods rigidly supported within the channel, each
positioned in one of a plurality of rows and one of a plurality of
columns of the fuel rods, the fuel rods including both full-length
rods and part-length rods; and the part-length rods distributed in
two rod groups including: a first rod group having two sub-groups
each having three part-length rods arranged in a triangular-shape,
each sub-group positioned proximate to each of the fluid passages;
and a second rod group having part-length rods each positioned
within and proximate to the perimeter wall, the second rod group
including a plurality of pairs of proximately arranged part-length
rods; wherein any of the part-length rods of the first rod group
are spatially separated from any of the part length rods of the
second rod group by at least two of the full-length rods.
23. A fuel bundle, comprising: a generally hollow channel having a
perimeter wall; a plurality of fuel rods including both full-length
and part-length fuel rods rigidly supported to the channel, each of
the fuel rods arranged in one a plurality of rows and one of a
plurality of columns of the fuel rods; each of the rows and each of
the columns disposed along a respective centerline, such that
proximate ones of the fuel rods on each of the centerlines define
each of a plurality of face-to-face pairs of fuel rods; and the
part-length fuel rods being separable into two rod groups,
including: a first rod group having two sub-groups each including
three part-length rods arranged in a triangular-shape, the two
sub-groups positioned proximate to each other and proximate to a
longitudinal centerline of the fuel bundle; and a second rod group
having part-length fuel rods each positioned proximate to the
perimeter wall, the second rod group being divisible into a
plurality of pairs of proximately positioned part-length rods;
wherein any of the part-length rods of the first rod group are
spatially separated from any of the part length rods of the second
rod group by at least two of the full-length rods; and wherein at
least one of the part-length fuel rods of each sub-group is
separable from one of the part length rods of the second rod group
by one of the face-to-face pairs of the fuel rods having two of the
full-length fuel rods.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application addresses similar subject matter to
co-pending and commonly assigned U.S. patent application Ser. No.
(unassigned) filed concurrently herewith, entitled AXIALLY
SEGREGATED PART-LENGTH FUEL RODS IN A REACTOR FUEL BUNDLE, by the
inventors of the subject application.
BACKGROUND OF THE INVENTION
[0002] b 1. Field of the Invention
[0003] The present invention relates in general to boiling water
reactors and more specifically to an apparatus and method of
construction for fuel bundles of boiling water reactors.
[0004] 2. Related Art
[0005] Fuel bundles for boiling water reactors typically each
provide a plurality of vertically stacked fuel rods. Common fuel
bundles or fuel assemblies provide a square or rectangular shaped
perimeter wall called a channel within which the fuel rods are
positioned. Reactor coolant flowing through the boiling water
reactor enters the bottom of the channel and passes vertically
upward and longitudinally over the fuel rods where it is heated to
form steam. The steam discharges from upper openings in the fuel
bundle. Boiling water reactors may contain several hundred fuel
bundles. One or more water passages are also commonly provided
within fuel bundle assembly to maintain a source of water to slow
down a sufficient quantity of neutrons to initiate and maintain
reactor criticality.
[0006] The highest potential operating energy capability for a
boiling water reactor is obtained if all fuel rods are full-length
fuel rods. The disadvantage of using 100% full-length fuel rods is
that reactor shut-down margin is not optimized. Following a reactor
shut-down, fission does not immediately stop. Neutrons continue to
fission, and it is necessary to trap sufficient neutrons to prevent
inadvertent reactor criticality. Shut-down margin is therefore a
sufficient percentage of trapped neutrons compared to fissioned
neutrons which prevents criticality. Shut-down margin is commonly
enhanced by distributing a quantity of part-length fuel rods in
each fuel bundle. A vacant volume above each part-length fuel rod
provides an additional water volume when the reactor is shut down.
These additional water volumes trap neutrons to provide increased
shut-down margin for the reactor. Common boiling water reactor fuel
bundles have part-length fuel rods evenly distributed about the
fluid flow channels but within an outer ring of full-length fuel
rods.
[0007] The known configurations of part-length fuel rods in a fuel
bundle do not achieve optimum reactor critical power and/or
shut-down margin.
SUMMARY OF THE INVENTION
[0008] According to a exemplary embodiment of the present
invention, a boiling water reactor comprises at least one fuel
bundle having a perimeter wall and opposed openings. At least one
fluid passage is disposed within the perimeter wall and extends
between the opposed openings. A plurality of fuel rods are disposed
within the perimeter wall, external to the fluid passage. The fuel
rods include both full-length rods and part-length rods. The
part-length rods are distributed in two rod groups. A first rod
group includes part-length rods each distributed adjacent to the
fluid passage. A second rod group includes part-length rods each
distributed within and immediately adjacent to the perimeter wall.
Each of the first and second groups includes at least one pair of
adjacent part-length rods.
[0009] The full-length fuel rods distributed about the perimeter of
the fuel bundle create a fuel rich zone. By distributing the
part-length fuel rods in groups and locating one of the rod groups
immediately adjacent to the perimeter wall of the fuel bundle,
locally increased volumes of water are provided both adjacent and
external to the full-length fuel rods. The part-length fuel rod
group located immediately adjacent to the perimeter is further
distributed in sub-groups each having one or, for example, pairs of
part-length fuel rods. Following reactor shut-down, water flowing
through the reactor accumulates above the grouped part-length fuel
rods to form water traps. The water traps formed above the
subgroups containing paired part-length fuel rods trap neutrons in
greater quantities due to a larger local volume of water adjacent
to the fuel rich zone of full-length fuel rods and a small
reduction of total fuel immediately adjacent to the perimeter wall.
Shut-down margin is therefore provided in a fuel bundle that better
utilizes the part-length fuel rods.
[0010] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the exemplary embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present invention will become more fully understood from
the detailed description and the accompanying drawings,
wherein:
[0012] FIG. 1 is a perspective view of a fuel bundle for a
exemplary embodiment of the present invention;
[0013] FIG. 2 is a sectioned view taken at Section 2-2 of FIG. 1
showing a exemplary arrangement of short-length fuel rods arranged
in two rod groups according to the present invention; and
[0014] FIG. 3 is a sectioned view similar to FIG. 2 showing an
alternate embodiment of the present invention having a single water
passage in lieu of two water passages and an alternate arrangement
of an external or perimeter rod group of the present invention.
DETAILED DESCRIPTION
[0015] The following description of the exemplary embodiment(s) is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
[0016] Referring to FIG. 1, a fuel bundle 10 of the present
invention is shown. The fuel bundle 10 includes a channel 12 which
encloses a plurality of fuel rods 14. Each of the fuel rods 14
contains a plurality of fuel pellets 16. The plurality of fuel rods
14 is divisible into a group of full-length fuel rods 18 and a
group of part-length fuel rods 20. Each of the fuel rods 14 has a
support end 21 supported by a lower rod support 22. An intermediate
rod support 24 is provided to support the approximate mid-span of
each of the full-length fuel rods 18 and a distal end of each of
the part-length fuel rods 20. An upper rod support 26 is provided
to support an upper end of each of the full-length fuel rods 18.
Additional rod supports (not shown) can be used to support the fuel
rods 14 as required.
[0017] A fuel bundle feed end 27 provides an inlet orifice 28
adjacent to the lower rod support 22 to allow an influx of water
into the fuel bundle 10. Water flows upwardly through the fuel
bundle 10 where it is heated to form steam. The steam discharges
from a plurality of outlet orifices 30 located at a discharge end
31 of the fuel bundle 10. A lifting member 32 provides a mechanical
lifting means for the fuel bundle 10 to install/remove the fuel
bundle 10 into/out-of a boiling water reactor having a plurality of
fuel bundles 10.
[0018] As best seen in FIG. 2, the fuel bundle 10 also includes an
inner perimeter wall 34 of the channel 12 housing the fuel rods 14
and one or more water passages 36. In the embodiment shown in FIG.
2, two water passages 36 are provided, each located adjacent to a
longitudinal centerline 37 of the fuel bundle 10. The fuel rods 14
are arranged in a 10.times.10 row-and-column configuration having
ten rows 43 and ten columns 45, within a generally square or
rectangular shaped fuel bundle 10. Each fuel rod 14 is adjacent at
least one other fuel rod 14 in either a "face-to-face" paired
arrangement or a "face diagonal" paired arrangement. The
face-to-face paired arrangement 49 results between two adjacent
fuel rods coaxially aligned along a common centerline 47 (only an
exemplary single centerline 47 is shown for clarity) taken through
either one of the rows 43 or the columns 45 of fuel rods 14. The
face diagonal arrangement results between two adjacent fuel rods
which are not coaxially aligned along either one of the common
centerlines 47 taken through the rows 43 or the columns 45 of fuel
rods 14.
[0019] The part-length fuel rods 20 are arranged in two groups. A
first rod group 38 is disposed adjacent to the water passages 36.
The first rod group 38 includes two subgroups of part-length rods
20 disposed on opposite sides of the water passages 36. Each
sub-group includes three part-length rods 20 forming two pairs of
adjacent part-length rods 20. A second rod group 40 is disposed
immediately adjacent to the inner perimeter wall 34 and is, for
example, distributed as shown in FIG. 2 in adjacent subgroup pairs
41 of part-length fuel rods 20. Each subgroup pair 41 of
part-length fuel rods 20, forming the second rod group 40, is
distributed approximately mid-span along each straight portion of
the inner perimeter wall 34. Each of the part-length fuel rods 20
which form the second rod group 40 are positioned in the
face-to-face arrangement with each adjacent part-length fuel rod
20.
[0020] A plurality of fuel bundles 10 are installed into a reactor
vessel (not shown) to form a boiling water reactor. When the
boiling water reactor is in a shutdown or non-critical operating
condition, water continuously flows (e.g., by externally provided
pumps) through each fuel bundle 10 to maintain proper cooling for
the reactor. During this condition, each of the water passages 36
fills with a water volume 42. A void above each of the part-length
fuel rods 20 also fills with water. These voids act as water traps
44 (see FIG. 1), which together with the water volume 42, trap
neutrons which continue to fission. By trapping neutrons, a
shutdown margin is provided to prevent the reactor from achieving
criticality at this undesired time. As best seen in FIG. 2, the
plurality of part-length fuel rods grouped into the first rod group
38 and the second rod group 40 distribute clumped groups of
part-length fuel rods such that clumped groups of water traps 44
are formed above sub-groups of the part-length fuel rods during the
shutdown condition. The channel 12 also includes a channel
connecting end 46 adjacent the channel feed end 27, which is used
to connect the channel 12 into a boiling water reactor vessel (not
shown). While the water passage 36 shown in this embodiment are
formed as a pair of circular shaped tubes 48, one or more circular
or other shaped tubes 48 may be used.
[0021] Referring now to FIG. 3, an alternate embodiment of the
present invention is shown. Items common with the embodiment of
FIG. 2, including but not limited to the supports, orifices,
lifting member, etc. are not shown for clarity. A fuel assembly 100
provides a plurality of full-length fuel rods 102 and a plurality
of part-length fuel rods 104. A single square-shaped water passage
106 is provided in this embodiment. As shown, the single water
passage 106 is located off center within the fuel bundle 100. It
should be noted that the water passage 106 can also be centrally
disposed within the fuel bundle 100. A channel 108 is formed in a
square shape for the alternate embodiment shown for the fuel bundle
100. The channel 108 has an inner perimeter wall 110 similar to
that shown in FIG. 2.
[0022] A 10.times.10 row-and-column arrangement of fuel rods is
provided by the embodiment shown in FIG. 3, similar to that shown
in FIG. 2. The invention is not limited to 10.times.10 arrangements
of fuel rods, therefore, the 10.times.10 configuration shown is an
exemplary arrangement of fuel rods. Similar to the arrangement of
FIG. 2, each of the part-length fuel rods 104 is distributed in one
of two rod groups. A first rod group 112 is disposed adjacent to
the water passage 106. The first rod group includes two sub-groups
disposed at one corner of the water passage 106. Each sub-group
includes a pair of adjacent part-length rods 104. A second rod
group 114 is distributed as paired part-length rods 116 and single
part-length rods 118. The second rod group 114 is distributed about
the perimeter of the fuel bundle 100 immediately adjacent to the
inner perimeter wall 110. The water passage 106 is shown positioned
off the longitudinal centerline 120 of the channel 108 and is
represented as a rectangular-shaped tube 122.
[0023] Similar to the fuel bundle 10 described above with respect
to FIGS. 1-2, the arrangement of the fuel bundle 100 provides the
second rod group 114 having the paired part-length rods 116 and the
single part-length rods 118 distributed approximately at the
mid-span of each of the walls of the channel 108. Based on the
10.times.10 fuel rod configuration and the offset location of the
water passage 106, single part-length rods 118 are located in a
near-bisecting position along the inner perimeter wall 110. The
location for the first rod group 112 and the second rod group 114
is exemplary in that the part-length rods 116, 118 can be
distributed in alternate configurations from those shown in FIG.
3.
[0024] By increasing the overall neutron absorption rate using the
first and second part-length rod groups of the present invention,
an improved shutdown margin for a boiling water reactor is
possible. The improved shutdown margin results by locally
increasing the size of water traps above part-length fuel rods by
pairing or grouping the part-length fuel rods on an external
boundary of the fuel bundle and adjacent to the water passages.
Selectively spaced, larger water traps in combination with the
water passages provides improved shutdown margin and reduced
potential for steam venting, without significantly reducing the
reactor critical power ratio.
[0025] The description of the invention is exemplary in nature and,
thus, variations that do not depart from the gist of the invention
are intended to be within the scope of the invention. For example,
circular and square water passage geometries are shown herein.
Other geometries are also possible, including water passages which
are formed simply by the elimination or relocation of fuel rods,
which permits water flow through regions of the fuel bundle where
fuel rods are not disposed. The water passages can therefore take
their shape depending upon the available geometry of the fuel
bundle. Rectangular, oval, cruciform or star-shaped water passages
can also be used, either having external passage walls or as free
flowing passages. Both single and paired water passages are shown
herein, however, additional quantities of water passages may also
be used.
[0026] It is also noted that a square fuel assembly is efficient
for arranging an 8.times.8, a 9.times.9, or a 10.times.10
row-and-channel configuration of fuel rods, however the invention
is not limited to a square fuel bundle. The invention can be used
for any fuel bundle geometry provided that the part-length fuel
rods are arranged in groups wherein at least one group is provided
immediately adjacent to an exterior or perimeter wall of the fuel
bundle, includes at least one part-length fuel rod, and is spaced
from any corner of the fuel bundle by at least one full-length fuel
rod. Such variations are not to be regarded as a departure from the
spirit and scope of the invention.
* * * * *